Effect of environmental temperature on hamster body fat composition

¹ Department of Physiology, University of California, Berkeley, California

Body fat content and the melting point and fatty acid composition of body fat of hamsters exposed to 35, 27, 20, 15, 10, and 6 C for 2 weeks were determined. The relationship between exposure temperature and body fat content and composition resembled that between environmental temperature and metabolic rate. Below the critical temperature, there was a progressive decrease in total body fat content and melting point accompanied by a decrease in the mole fraction of palmitic acid and an increase in the mole fraction of oleic acid. The softening of body fat in cold-exposed animals appears to be the result of an increased mobilization of depot fat in response to a higher metabolic rate in the cold, a mobilization which is at least partially selective with respect to individual fatty acids or triglycerides. Examination of changes in whole body composition revealed that 72% of the loss in body weight of hamsters exposed to 6 C was due to a decrease in body fat content. In contrast, the decrease in body fat content accounted for only 28% of the body weight loss of pair-fed hamsters kept at 27 C on reduced caloric intake to match the body weight loss experienced by cold-exposed animals. It appears, therefore, that cold exposure induces a more effective fat depot mobilization than does reduced caloric intake.

Submitted on February 3, 1964

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